Jonesville Millpond Dam Reservoir Report
Last Updated: December 5, 2025
Jonesville Millpond Dam, located in Jonesville, Michigan, stands as a historic structure completed in 1872 with a primary purpose of providing recreational opportunities.
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Summary
This earth dam, towering at a height of 9 feet and stretching out to 500 feet in length, creates a picturesque millpond along the Saint Joseph River. With a storage capacity of 170 acre-feet and a surface area of 35 acres, this dam contributes to the local landscape and provides a tranquil setting for visitors to enjoy.
Despite its age, Jonesville Millpond Dam has a low hazard potential and is currently not rated for its condition. The dam's spillway, with a width of 50 feet, is uncontrolled, allowing for natural water flow regulation. While it has not been inspected since 1994, with an inspection frequency of 5 years, there is a moderate risk associated with the structure, indicating a need for continued monitoring and potential risk management measures in the future. As an integral part of the local community, the dam's role in providing recreational opportunities and its historical significance make it a valuable asset worth preserving for future generations to enjoy.
Year Completed |
1872 |
Dam Length |
500 |
Dam Height |
9 |
River Or Stream |
Saint Joseph River |
Primary Dam Type |
Earth |
Surface Area |
35 |
Hydraulic Height |
9 |
Drainage Area |
63 |
Nid Storage |
170 |
Structural Height |
9 |
Hazard Potential |
Low |
Nid Height |
9 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Jonesville Millpond Dam